Major crossroads are usually controlled by traffic lights. Vehicles are required to stop on the red light, and are free to go on the green light. Frequent stops not only waste time, but also waste fuel due to excess fuel being injected into the engine when accelerating, from rest when the vehicle starts again on the green light. The fuel is not burned completely which causes air pollution. In addition, traffic accidents occur frequently at crossroads.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional crossroad.